This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Our long term goals are to elucidate polysaccharide structures and their interactions with solvent and solute molecules as well as the synergistic interactions in mixed polysaccharide systems towards gaining insights about their structure-function relationships. In this regard, the current proposal is about determining the molecular architecture of a number of biologically important and industrially useful polysaccharides. The study includes the samples from algal (iota, kappa and lambda carrageenans);bacterial (gellan analog and cepacian);fungal (glucuronoxylomannan);plant (rhamnogalacturonan);wood (galactoglucomannan) and a binary system (bacterial xanthan:plant glucomannan and bacterial acetan:plant glucomannan). More recently, we demonstrated that small molecules such as benzocaine and thymol can be entrapped in crystalline iota-carrageenan network leading to polymeric cocrystals (unpublished results). Thus, our second aim is centered on the characterization of polymeric cocrystals (obtained from several FDA approved polysaccharides combined with small drug molecules) and determining their three-dimensional structures. It is hoped that these results would be helpful in understanding the polysaccharide:drug interactions towards the development of controlled drug releasing carriers. These polysaccharides or polysaccharide complexes have an inherent tendency to form helical structures with only limited lateral ordering and are not amenable for growing single crystals. Hence, fiber diffraction is the only method of choice for visualizing their three-dimensional organization. Such structural information is essential for understanding their interactions with solvent and solute molecules as well as with other polysaccharides for their effective utilization in food and pharmaceutical applications. The results will further highlight the conformational space available to polysaccharides as they occur in glycosaminoglycans and cellular walls.